Myanmar opposition leader Aung San Suu Kyi declared Saturday that the Nobel Peace Prize she won while under house arrest 21 years ago helped to shatter her sense of isolation and ensured that the world would demand democracy in her military-controlled homeland.

Suu Kyi received two standing ovations inside Oslo's city hall as she gave her long-delayed acceptance speech to the Norwegian Nobel Committee in front of Norway's King Harald, Queen Sonja and about 600 dignitaries. The 66-year-old champion of political freedom praised the power of her 1991 Nobel honor both for saving her from the depths of personal despair and shining an enduring spotlight on injustices in distant Myanmar.

"Often during my days of house arrest, it felt as though I were no longer a part of the real world," she said to a silent chamber, which was lined with rainbows of freshly cut zinnias and towers of orchids and gladiolas. "There was the house which was my world. There was the world of others who also were not free but who were together in prison as a community. And there was the world of the free. Each one was a different planet pursuing its own separate course in an indifferent universe.

"What the Nobel Peace Prize did was to draw me once again into the world of other human beings, outside the isolated area in which I lived, to restore a sense of reality to me. ... And what was more important, the Nobel Prize had drawn the attention of the world to the struggle for democracy and human rights in Burma. We were not going to be forgotten," she said during her 40-minute oration.

Suu Kyi, who since winning freedom in 2010 has led her National League for Democracy party into opposition in Myanmar's parliament, offered cautious support for the first tentative steps toward democratic reform in her country. But she said progress would depend both on maintaining foreign pressure on the army-backed government — and on carefully managing the ethnic tensions threatening to tear apart the country.

"If I advocate cautious optimism, it is not because I do not have faith in the future, but because I do not want to encourage blind faith. Without faith in the future, without the conviction that democratic values and fundamental human rights are not only necessary but possible for our society, our movement could not have been sustained throughout the destroying years," she said, referring to the past two decades since Myanmar's military leaders rejected her party's overwhelming triumph in 1990 elections, one year after Suu Kyi's own imprisonment.

Thorbjorn Jagland, chairman of the Norwegian Nobel Committee, introduced Suu Kyi as a leader of "awe-inspiring tenacity, sacrifice and firmness of principle."

"In your isolation, you have become a moral leader for the whole world," he said from the podium, turning to the seated Suu Kyi.

"Your voice became increasingly clear the more the military regime tried to isolate you. Your cause mobilized your people and prevailed over a massive military junta. Whenever your name is mentioned or when you speak, your words bring new energy and hope to the entire world," Jagland said to applause.

Suu Kyi, in a traditional Burmese gown of purple, lilac and ivory, offered only a stoic Mona Lisa smile at the end of her speech, greeted with a 2-minute ovation. As on her previous public events this week in Switzerland and Norway, she spoke with a voice of unerring crisp diction but a physical presence bordering on exhaustion.

Yet Saturday's schedule offered no letup. She left the city hall for the neighboring Nobel Peace Center where artists had designed an interactive display called "Mother Democracy" chronicling the highlights of her life. She chatted in Burmese with about 300 refugees from Myanmar granted asylum in Norway.

Then she addressed a public rally that attracted about 10,000 Oslo locals and tourists, many from foreign cruise liners docked along the capital's nearby shoreline. Many waved Norwegian flags and leaflets bearing Suu Kyi'simage as she thanked the Norwegian people for giving so many of her countrymen and women sanctuary from oppression.

Smiling with delight as church bells tolled, she also led the crowd in Burmese chants wishing everyone peace and happiness.

"Suu Kyi is such an incredible person. It's a blessing to be here, to get the once-in-a-lifetime chance to see her, to hear her," said Javier Rodriguez, 50, an airline steward from Los Angeles who happened to be on an Oslo layover and staked out the peace center before Suu Kyi's arrival.

"There's so few people in the world willing to sacrifice everything for justice and peace. She's in the same league as Nelson Mandela. Everyone should cherish and honor her," he said.

In her Nobel speech, Suu Kyi related her long experience of state-ordered isolation to key precepts of her Buddhist faith, particularly two forms of suffering: Being forced to live apart from loved ones, and being forced to live among those one dislikes. She referred only fleetingly to the Myanmar authorities' refusal to permit her husband, the Buddhist scholar Michael Aris, to see her from 1995 until his death from cancer in 1999.

Instead she emphasized the continued suffering of others. She won spontaneous applause from the crowd as she appealed for foreign governments to understand that many hundreds of political prisoners remain in Myanmar.

"It is to be feared that because the best known detainees have been released, the remainder, the unknown ones, will be forgotten. I am standing here because I was once a prisoner of conscience. As you look at me and listen to me, please remember the often repeated truth that one prisoner of conscience is one too many," she said.

She said it was unrealistic to expect the world ever to reach a state of "absolute peace," yet mankind must be compelled to pursue the goal "as a traveler in a desert fixes his eyes on the one guiding star that will lead him to salvation. Even if we do not achieve perfect peace on earth, because perfect peace is not of this earth, common endeavors to gain peace will unite individuals and nations in trust and friendship, and help us to make our human community safer and kinder."

And Suu Kyi praised the value of simple, every-day acts of human kindness as the most powerful force in promoting peace anywhere. " Every kindness I received, small or big," she said, referring to her 15 years of house arrest or imprisonment, "convinced me that there could never be enough of it in our world."

On Sunday she heads to the Norwegian city of Bergen to meet charities and members of Norway's Burmese refugee community, then on Monday speaks alongside U2 singer Bono before the pair fly to Dublin, Ireland, for a celebrity-studded concert in her honor. On Tuesday she starts engagements in England, including a visit to her Oxford University alma mater and a speech to the joint houses of Parliament.